Most walk-away borrowers are good credit risks with high FICO scores. One Florida couple paid $1.4 million for a house which is now worth $400,000. They are still paying, but not all borrowers would stick with that mortgage.

Consumers are adapting the rationality of professional investors. An investor who purchases an office building will often use a company to make the purchase and borrow the money. If the value fell by half while the mortgage is 70% of the original price, and if the loan is not personally guaranteed, the investor might send in the keys and wish the lender good luck.